Gravity Signaling in Flowering Plant Roots

Abstract

Roots typically grow downward into the soil where they anchor the plant and take up water and nutrients necessary for plant growth and development. While the primary roots usually grow vertically downward, laterals often follow a gravity set point angle that allows them to explore the surrounding environment. These responses can be modified by developmental and environmental cues. This review discusses the molecular mechanisms that govern root gravitropism in flowering plant roots. In this system, the primary site of gravity sensing within the root cap is physically separated from the site of curvature response at the elongation zone. Gravity sensing involves the sedimentation of starch-filled plastids (statoliths) within the columella cells of the root cap (the statocytes), which triggers a relocalization of plasma membrane-associated PIN auxin efflux facilitators to the lower side of the cell. This process is associated with the recruitment of RLD regulators of vesicular trafficking to the lower membrane by LAZY proteins. PIN relocalization leads to the formation of a lateral gradient of auxin across the root cap. Upon transmission to the elongation zone, this auxin gradient triggers a downward curvature. We review the molecular mechanisms that control this process in primary roots and discuss recent insights into the regulation of oblique growth in lateral roots and its impact on root-system architecture, soil exploration and plant adaptation to stressful environments.

Fourteen Stations of Auxin

“…One of the best-characterized examples of this concept is gravitropism, which aligns the growth of plants with a gravity vector. The gravity is perceived in seed plants by sedimentation of starch-containing amyloplasts (statoliths) in root columella or shoot starch sheath (for review, see Su et al 2020). As shown in Arabidopsis, several PIN proteins are expressed in the very same cells and polarize to the bottom cell sides after gravistimulation (Friml et al 2002b;Kleine-Vehn et al 2010;Rakusová et al 2011).…”

Auxin and Root Gravitropism: Addressing Basic Cellular Processes by Exploiting a Defined Growth Response

“…The role of actin in the gravitropic sensing response has been studied for many years and was proposed to influence the velocity of statolith sedimentation [ 26 ]. From that, it appears that the dynamics in the intracellular statolith distribution, next to statolith-plasma membrane contacts, contributes to initial gravity signaling [ 27 ]. Furthermore, and to complicate matters, the gravitropic response in its entirety is not due only to signal perception in the root cap, as it has been shown that events in the elongation zone play a role as well [ 28 , 29 ].…”

Creosote Bush (Larrea tridentata) Phytochemical Traits and its Different uses: A Review

“…Recently, the resistance to several commercial fungicide products has gained interest for the use of natural original compounds, as an alternative for the control of fungi diseases since some of them inhibit fungi growth and have demonstrated to be effective on in vitro and in vivo conditions [55][56][57][58]. Particularly the creosote bush has been studied for its antifungal action, on several occasions under in vitro conditions at least 17 phytopathogenic fungi of economic importance have been tested, on in vivo studies as ground vegetative material or as an extract incorporated to the soil to control 6 fungi in agriculture crops [59][60][61].…”